It is known to enhance load carrying capacity of a post assembly of a trellis or fence system by securing a stay post diagonally between first and second upright posts, which are then placed under tension to support the fence or trellis. For that purpose, a notch may be formed in either end of the stay post to assist in locating the stay post relative to the upright posts. However, the structural integrity of the stay post may be compromised as a result, leading to potential failure of the post assembly.